The hydroesterification or hydrocarbomethoxylation of olefins catalyzed by cobalt catalysts is known, being described for example in U.S. Pat. No. 2,542,767. The use of a small amount of pyridine in combination with hydrogen is known to improve the selectivity of the hydroesterification of propylene. This is described by A. Matsuda and H. Uchida in Chem. Soc. Japan Bull. 38, 710-715 (1965). Relatively large amounts of pyridine alone are also known to promote propylene hydroesterification as disclosed by V. Gankin et al, in Zh. P. Kh. 40, 1862-1864 (1967).
Other discussions of the reaction of olefinic materials with CO in the presence of cobalt catalyst and a pyridine are contained in U.S. Pat. No. 3,507,891, in U.S.S.R. Pat. No. 173,754 (Sept. 25, 1965), and in Japanese Pat. No. 12,854 (July 21, 1966); in Chem. Abstracts, Vol. 68, 12411b (1968) (page 1169); by Ghankin et al, Zh. Prikl. Khim. (Leningrad) 14 (11) 2582-5, Nov. 1968; and by G. Natta, Brennstoff-Chem., 36, 176 (1955).
One of the seldom-mentioned problems of the prior art hydroesterification processes is catalyst inactivation. This problem is not readily appreciated in laboratory scale tests; however, it shows up in large scale operation. Until now, it has been necessary to replace the catalyst as its activity decreases. Since the provision of active catalyst on the scale necessary for commercial operations represents a significant factor in the cost of the product, it is desired to provide a way to reduce the rate of catalyst inactivation. The present invention provides a way to increase catalyst life by performing the process in a manner that is different from the usual prior art method of processing. In the past, it has been the customary practice to feed initially all of the olefin and lower alcohol required for the reaction including even a large excess of alcohol (100 percent excess or more) above the stoichiometric amount required for the reaction.